What are online games that are free and there is NO need to download

An online game is a game played over some forms of computer network. This almost always means the Internet or equivalent technology.
Nowadays, a large number of browser games are online games which are totally free and don't need to download any client, just like The Wars game.
You'd better to give a try this game web site, where are listing many online games just as you said.
http://wars.swagblack.com/webgamethewars.aspx